U.S. Pat. No. 3,097,366 describes and illustrates a heart pump comprising two elastic bags joined by a one-way valve and contained in a casing. The ventricle bag is periodically squeezed between a driven plate and the casing wall to pump the blood. The ventricle bag is cemented to the driven plate, which is resiliently urged in a direction to expand the ventricle bag between driven pulses for forced refilling. The atrium bag is larger than the ventricle bag so inflow during the pumping stroke can occur because of partial collapse of the atrium bag during each outflow pulse. The only way to regulate this heart pump is to vary the speed of the drive (pulse).
The heart pump of U.S. Pat. No. 3,656,873, which is intended for temporary use in heart surgery, also has two bag-like flexible containers with a one-way valve at the outlet of the bag that serves as the ventricle. Each flexible container is mounted in a separate rigid container so that the outside of such flexible container can be exposed cyclically to pneumatic pressure. The ventricle container is compressed intermittently to give a pulsating flow.
The atrium container is subjected to pressure or vacuum, which determines the intake of blood. To the extent that the pressure of the incoming blood exceeds the pressure outside the atrium container, blood will be taken in. The pressure outside the ventricle container is varied, and blood is admitted from the atrium if the pressure in the ventricle is lower than in the atrium, in which case the one-way valve allows the blood to pass until the pulsation causes the pressure in the ventricle volume to exceed the atrium pressure. It is evident that this design can be regulated by varying the frequency and pressure of the pneumatic pulses, but it cannot be adjusted to a constant setting of the intake velocity because the atrium volume is independent of the volume of the ventricle.
U.S.S.R. (Russian) Pat. No. 944815 (1981) describes and shows a blood pump comprising either a ventricle chamber or both an atrium chamber and ventricle chamber, each of bulbous shape and having a flexible walls, received in a casing. The ventricle chamber is periodically and repeatedly compressed by movement of the armature of a linear electric motor working through a convexly curved annular drive shoe that is connected to a valve plate at the inlet to the ventricle chamber. The return stroke is provided by a spring. The arrangement is such that the intake stroke is strongly influenced by the spring. Hence, the device is essentially a positive displacement pump, the output of which can be varied only by changing the pulse rate.
The present invention has arisen out of the discovery of the present inventor that the human heart does not work in the way it is generally believed to. Because this constitutes part of the background of the invention, a short explanation will be given here in order to make the invention easier to understand. A more detailed description of the inventor's findings is found in Lundback, S. Cardiac Pumping and Function of the Ventricular Septum. Supplementum 550 1986 to Acta Physiologica Scandinavica (ISBN 91-7900-066-5).
Starting from the observation made in, inter alia, ultrasonic examinations that the volume of the heart during a beat often only varies by less than 10%, together with the observation that the incoming blood is not appreciably pulsating and the blood coming out is vigorously pulsating, it has been possible to predict and to clinically ascertain that what happens when the heart is beating is that the heart muscle at contraction is pulling the dividing walls at the atria, including the heart valves, down towards the heart apex. When the heart muscle thereafter relaxes, the plane of the valves will be pressed upwards, not by muscle power but by the dynamic and static forces of the inflowing blood and by elastic components within and outside the heart. Thus the volumes of the ventricles will decrease and the volumes of the atria will increase during the systolic phase, and the sum of these volumes is somewhat decreasing and the outer shape of the heart thus decreases in the systolic phase. More blood than is coming in is thus pumped out during systole. The inflow into the atria, however, continues during systole by enlargement of the atria. During diastole, the valves in the aorta and the pulmonary artery close, and the inflow into the atria continues because the total heart volume is somewhat increasing. The plane of the valves returns upwards, more or less depending on the refilling volume, whereby the displacement volume in the subsequent ventricular systole is determined by the amount of blood flowing into the heart during both systole and diastole. These findings, in conjunction with another discovery concerning the regulating function of the cardiac septum, must be considered a surprise and might induce a true paradigm shift within the sciences concerned.
Moreover, it can now be explained how the heart is filled during diastole, i.e., what power is causing variation in the volume of the heart. The fact is that the heart muscle is constituted in such way that it has a capability of contraction, but after contraction has to be stretched by the aid of another force. According to the inventor's findings, this force is a hydrodynamic impact-type force caused by kinetic energy imparted to the blood in the heart during systole, which at the end of systole and at the closing of aortic and pulmonic valves is transformed to a pressure which has a tendency to increase the ventricular volume by, among other things, pressing the valve plane upwards.